salon balayage hair due gone wrong! pls help.. too brassy with looks yellow/orange

I'd approach them! It's uncomfortable but you've paid a lot of money at the end of the day.

I wouldn't recommend trying to totally fix it yourself however I get my hair balayaged and I naturally have a lot of warmth in my hair so I'm prone to going brassy. I use the Jerome Russell silver toner (it's £3, I only get about 3 uses per bottle but it's amazing) and Aussie Blonde Hydration shampoo and conditioner and together they make my hair a lovely colour- they tone down the brassiness which blends my blonde much better with my light brown roots. Depending on the colour of your hair you could benefit from a toner. Just don't bleach it yourself, discuss with your hairdressers if you are going to go back or not and if you put anything on your hair to tone or colour it, make sure you tell a hairdresser what you've been using!

Thank you so much for your advice. Yes I think I will go back but just so awkward as they were correcting a previously bad balayage and spent ages on it.. they tried to convince me it was nice whilst I was there and was in the chair for 6 hours!! ha ha. But I think it is really bad and just looks like I have copper highlights with bleached blonde highlights.. just doesnt look good. I wanted blended roots, sunkissed look but it just looks grown out and v bad.
They were so nice so just need to phrase it carefully.. do you think call or send an email with pictures?

Personally I'd call them and speak to an actual person so you can get your tone across better (as in emails can sometimes sound a tad arsey but if you can explain over the phone they can tell you genuinely are just trying to fix the problem). Hopefully they'll be understanding- after all it looks bad on them and they'll have lost a customer if you think they can't do a good job!

Possibly part of the problem is that 'sunkissed' is quite golden and that can lead to more yellow blondes? I feel you on the copper and yellow tones though- first time I had my hair bleached I looked like the unholy love child of Garfield and Big Bird. Just took a bit of time, a lot more bleach and a good toner